1. Field of the Invention
This invention relates generally to switches and more particularly to switch systems used to control power to an industrial machine.
2. Description of the Prior Art
Previously switch systems used to control industrial machines have employed either optical switches or capacitance touch plate switches. An example of an optical switch system is disclosed in U.S. Pat. No. 4,939,358, and an example of a touch plate system is disclosed in U.S. Pat. No. 4,412,268. However, these systems can be triggered unintentionally and no system presented to date has improved on the safety of these switch systems. Typical causes of false triggering of the optical switch are an operator's sleeve, insects or dust; and external RF disturbances can affect the touch plate capacitance switch. Also, in spite of safety precautions, some operators will attempt to trick the switches by placing an object in the switch opening to trip the optical switch or will use a capacitive device to trip the touch plate switch.